Structural component and method of manufacture

ABSTRACT

A structural component is provided comprising a base member comprising at least two sidewalls and a space therebetween, the base member having a predetermined curvilinear configuration formed using hot stretch forming. The structural component comprises at least one reinforcing member linear friction welded to the at least two sidewalls so that the reinforcing member is positioned at least partially within the space between the at least two sidewalls.

CROSS-REFERENCE TO PRIORITY APPLICATION

This application is a continuation of U.S. patent application Ser. No.13/279,108 for a STRUCTURAL COMPONENT AND METHOD OF MANUFACTURE, filedOct. 21, 2011, (and published Apr. 26, 2012 as U.S. Patent ApplicationPublication No. 2012/0100387), which itself claims the benefit of U.S.patent application Ser. No. 61/405,914 for a STRUCTURAL COMPONENT ANDMETHOD OF MANUFACTURE, filed Oct. 22, 2010. Each of the foregoing patentapplications and publication is hereby incorporated by reference in itsentirety.

FIELD

The invention generally relates to the field of structural components,and more particularly, embodiments of the present invention relate to animproved structural component comprising a base member and at least onereinforcing member affixed thereto and methods of manufacture therefor.

BACKGROUND

Various industries, including the aerospace industry, have a need forcomplex structural components that are relatively free of residualstresses and are capable of being machined without failing. Inparticular, there is a need for curved finish machined components havinggenerally L-shaped or U-shaped cross-sectional profiles that includevarious features that cause inconsistencies in the cross-sectionalprofile along the length of the component, such as gussets, fins, andtabs. Unfortunately, forming an L-shaped or U-shaped piece into a curvedcomponent and adding gussets, fins, and tabs using conventional methodssuch as forging, laser welding, fusion welding, and other known methodsresults in a finished component that has unacceptable levels of residualstress that remain in the component due, in principal part, to theinhomogenous deformation to which the component has been subjectedduring the forming and manufacturing process. Components having residualstresses are prone to failure and/or shape changes during furthermachining or use, and has weaker bonds between the base piece and thecombined elements than would be preferred. Because of these drawbacks,these components must be formed by utilizing an original extrusion orrolled shape that includes the additional features over the entirelength of the piece, and removing material from the piece as needed todefine the desired features. This method not only significantlyincreases the weight and cost of the raw material required tomanufacture the component, but also substantially increases the amountof time required to manufacture the component, as removing theunnecessary material from the rest of the cross section during finalmachining is a timely process requiring relative expensive machinery andskilled expertise. Thus, there remains a need for improved structuralcomponents and methods of manufacture of structural components thatreduce both the amount of raw material required and the subsequentmachining operations.

SUMMARY

The present invention provides structural components and associatedmethods of manufacture. According to one embodiment, the method formanufacturing a structural component comprises forming a base membersuch that the base member comprises at least two sidewalls and a spacetherebetween. The base member is hot stretch formed so that the basemember has a predetermined curvilinear configuration. At least onereinforcing member is linear friction welded to the at least twosidewalls so that the reinforcing member is positioned at leastpartially within the space between the at least two sidewalls.

According to another embodiment of the present invention, the method formanufacturing a structural component comprises positioning a profilecomprising at least two sidewalls and a space therebetween in aheat-insulating enclosure in which a die is disposed such that theprofile is in forming proximity to the die. The profile is resistanceheated to a working temperature by passing electrical current throughthe profile. The profile and die are moved relative to each other whilethe profile is at the working temperature, thereby forming a base memberhaving a predetermined curvilinear configuration. The curvilinear basemember is mounted on a mounting assembly. A reinforcing member isaffixed to the at least two sidewalls using linear friction welding sothat the reinforcing member is positioned at least partially within thespace between the at least two sidewalls. In one embodiment, theaffixing step comprises positioning the reinforcing member in contactwith the base member to define a first interface between the reinforcingmember and a first sidewall and a second interface between thereinforcing member and a second sidewall; applying a first forge load atan angle relative to the first weld interface and a second forge load atan angle relative to the second weld interface, the first and secondforge loads having predetermined magnitudes; oscillating the reinforcingmember at a predetermined oscillation amplitude to heat the reinforcingmember and the base member; reducing the oscillation amplitude to zero;and increasing the first and second forge loads to predeterminedset-points and maintaining for a predetermined period of time; andreducing the first and second forge loads to zero.

According to one embodiment of the methods disclosed herein, at leastone of the base member is and reinforcing member is formed of titaniumor a titanium alloy. According to another embodiment of the methodsdisclosed herein, at least one of the base member and reinforcing memberis formed of aluminum or an aluminum alloy. According to anotherembodiment of the methods disclosed herein, the base member andreinforcing member are formed of the same material. According to yetanother embodiment of the methods disclosed herein, the base member andreinforcing member are formed of different materials.

According to one embodiment of the present invention, the structuralcomponent comprises a base member comprising at least two sidewalls anda space therebetween, the base member having a predetermined curvilinearconfiguration formed using hot stretch forming. The structural componentfurther comprises at least one reinforcing member linear friction weldedto the at least two sidewalls so that the reinforcing member ispositioned at least partially within the space between the at least twosidewalls.

According to another embodiment of the present invention, the structuralcomponent comprises a base member, wherein the base member is formed bypositioning a profile comprising at least two sidewalls and a spacetherebetween in a heat-insulating enclosure in which a die is disposedsuch that the profile is in forming proximity to the die; resistanceheating the profile to a working temperature by passing electricalcurrent through the profile; and moving the profile and the die relativeto each other while the profile is at the working temperature. Thestructural component comprises at least one reinforcing member affixedto the base member, wherein the reinforcing member is affixed by:positioning the reinforcing member in contact with the base member todefine a first interface between the reinforcing member and a firstsidewall and a second interface between the reinforcing member and asecond sidewall; applying a first forge load at an angle relative to thefirst weld interface and a second forge load at an angle relative to thesecond weld interface, the first and second forge loads havingpredetermined magnitudes; oscillating the reinforcing member at apredetermined oscillation amplitude to heat the reinforcing member andthe base member; reducing the oscillation amplitude to zero; increasingthe first and second forge loads to predetermined set-points andmaintaining for a predetermined period of time; and reducing the firstand second forge loads to zero.

According to one embodiment of the present invention, at least one ofthe base member and the reinforcing member is formed of titanium or atitanium alloy. According to another embodiment of the presentinvention, at least one of the base member and the reinforcing member isformed of aluminum or an aluminum alloy. According to another embodimentof the present invention, the base member and reinforcing member areformed of the same material. According to yet another embodiment of thepresent invention, the base member and reinforcing member are formed ofdifferent materials.

Thus, there has been provided improved structural components and methodsof manufacture of structural components that reduce both the amount ofraw material required and the subsequent machining operations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a structural component,according to one embodiment of the present invention;

FIG. 2 is a perspective view illustrating a profile, according to oneembodiment of the present invention;

FIG. 3 is a perspective view illustrating a stretching forming apparatusthat can be used to form the profile of FIG. 2, according to oneembodiment of the present invention;

FIG. 4 is a partial-cutaway view illustrating a die that is disposedinside a die enclosure of the stretch forming apparatus of FIG. 3,according to one embodiment of the present invention;

FIG. 5 is a perspective view illustrating a linear friction weldingmachine, according to one embodiment of the present invention;

FIG. 6 is a perspective view illustrating the linear friction weldingmachine of FIG. 1; and

FIG. 7 is a perspective view illustrating the forging forces applied toa reinforcing member to be right-angle welded to profile that has beenformed.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Embodiments of the present invention now will be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all, embodiments of the invention are shown. Indeed, theinvention may be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will satisfy applicablelegal requirements. Like numbers refer to like elements throughout.

Referring to FIG. 1, a structural component 10 in accordance withembodiments of the present invention is provided. According to someembodiments, and as shown in FIG. 1, the structural component 10comprises a base member 12 and at least one reinforcing member 14. Insome embodiments, the structural component 10 comprises a plurality ofreinforcing members 14. In some embodiments, the structural component 10is comprised of metal. For example, the base member 12 and/or the atleast one reinforcing member 14 may be comprised of titanium or atitanium alloy. In another embodiment, the base member 12 and/or the atleast one reinforcing member 14 may be comprised of aluminum or analuminum alloy

In some embodiments, the base member 12 comprises a bottom wall 16 andone or more sidewalls 18 such that the cross-sectional profile of thebase member 12 is an L-shape, a U-shape, a C-shape, a T-shape, or anyother shape defining an open area within which reinforcing members 14may be affixed to the base member 12. Although the terms “bottom wall”and “sidewall” are used herein to refer to portions of the base member12, these terms are not being used to denote any particular directionalorientation for the base member, i.e., the “bottom wall” and/or the“sidewall” each comprises a generic “sidewall” that can comprise alateral sidewall, top wall or bottom wall when the base member isinstalled in its intended operating environment and orientation.According to some embodiments, and as shown in FIG. 1, the base member12 has a curvilinear shape such that the base member 12 is curved aboutone or more axes normal to the plane of the bottom wall 16, where thebottom wall 16 remains substantially planar. In some embodiments, thestructural component 10 may further comprise one or more tabs 22 or fins24 or other protuberances. Such tabs 22 and fins 24 or protuberance maybe formed integrally with the base member 12 or may be affixed to thebase member 12 as discussed in more detail below.

According to some embodiments, the base member 12 is formed by applyinga stretch forming process to a profile 20, i.e., a piece of material,such as metal. The profile 20 may be formed through extrusion, aroll-forged method, or other manufacturing process. Thus, in someembodiments, the base member 12 is formed from a profile having thedesired cross-sectional shape for the base member 12, as defined by abottom wall 16 and one or more sidewalls 18. As illustrated in FIG. 2,the profile 20 has a substantially straight shape prior to forming. Inorder to achieve the curvilinear shape of the base member 12, theprofile 20 is heated and formed within a stretch forming apparatus. SeeU.S. Pat. No. 7,669,452 to Polen et al. for a general discussion ofstretch forming, the entire contents of which are incorporated herein byreference.

According to some embodiments, and as illustrated in FIG. 3, the stretchforming apparatus 30 comprises a main frame 32, a die mounting surface34, and first and second opposed swing arms 36A, 36B (also referred toherein as swing arms 36). The swing arms 36 are pivotally mounted to themain frame 32 and are coupled to hydraulic forming cylinders 38A, 38B or38, and carry hydraulic tension cylinders 40A, 40B (also referred toherein as tension cylinders 40), which in turn have hydraulicallyoperable opposed jaw assemblies 42A, 42B (also referred to herein asjaws 42) mounted thereto. Appropriate pumps, valving, and controlcomponents may be provided for supplying pressurized hydraulic fluid tothe forming cylinders 38, tension cylinders 40, and jaws 42A, 42B. Inaddition to the foregoing components, a heat-insulating die enclosure 44is mounted to the die mounting surface 34 between the jaw assemblies 42Aand 42B. In some embodiments, the die enclosure 44 comprises first andsecond aligned and opposed openings that are configured to accommodatethe ends of the profile 20. Furthermore, the die enclosure 44 may beopened to place the profile 20 therein and remove it therefrom, but whenclosed is fully enclosed except for the two openings for the ends of theprofile 20. In some embodiments, and with reference now to FIG. 4, a die46 is disposed inside the die enclosure 44. The die 46 is a relativelymassive body with a working face 48 that is shaped so that a selectedcurve is imparted to the profile 20 as it is bent around the die 46, asdescribed in more detail below. According to some embodiments, thecross-section of the working face 48 generally conforms to thecross-sectional shape of the profile 20, such that the profile 20 may beplaced flush against the working face 48 of the die 46.

According to some embodiments, in order to form the profile 20 into thebase member 12 of the structural component 10 using the stretch formingapparatus 30, the profile 20 is positioned in the die enclosure 44 informing proximity to the working face 48 of the die 46. The profile 20is placed in the die enclosure 44 such that the opposite ends of theprofile 20 extend through the respective first and second openings ofthe die enclosure 44 and the remaining portion of the profile 20 issubstantially fully enclosed within the die enclosure 44. The jaws 42are then clamped down against the respective opposite ends of theprofile 20 that are protruding from the openings in the die enclosure44. According to some embodiments, the profile 20 is electricallyinsulated from the components of the assembly 30, including the jaws 42and the die 46. For example, the die 46 may be constructed from multiplepieces of a ceramic material such as fused silica. The die 46 may alsobe fabricated from other refractory materials, or from non-insulatingmaterials which are then coated or encased by an insulating layer

Once the profile 20 is placed in the assembly and the jaws 42 areclamped on the opposing ends, according to some embodiments, current ispassed through the profile 20, causing resistance heating thereof. Aconnector from a current source may be placed on each end of the profile20 to provide the resistance heating. In other embodiments, the heatingcurrent connection may be directly through the jaws 42, as describedabove. By using thermocouples or other temperature-sensing devices, thecurrent source can be programmable-logic-controller (“PLC”) controlledusing a temperature feedback signal. This will allow proper ramp ratesfor rapid but uniform heating, as well as allow for the retardation ofcurrent once the profile 20 reaches the target temperature. Aproportional-integral-derivative (“PID”) control loop of a known typecan be provided to allow for adjustments to be automatically made as thetemperature of the profile 20 varies during the forming cycle. Thiscontrol may be active and programmable during the forming cycle. Thus,closed loop controlled heating of profile 20 continues, utilizingfeedback from the thermocouples or other temperature sensors, until thedesired working temperature set point is reached. The rate of heating ofthe profile 20 to the set point is determined taking into account thecross-section and length of the profile 20, as well as relevantthermocouple feedback. During the stretch-forming operation, the profile20 will be heated to temperatures of about 538 degrees Celsius (about1000 degrees Fahrenheit) or greater.

Once the working temperature has been reached, forming of the profile 20into the base member 12 can begin. According to some embodiments, thetension cylinders 40 stretch the profile 20 longitudinally to thedesired point, and the forming cylinders 38 pivot the swing arms 36inward to wrap the profile 20 against the die 46 while the workingtemperature is controlled as required. Thus, the die 46 imparts thecurvilinear shape to the base member 12. The stretch rates, dwell timesat various positions, and temperature changes can be controlled viafeedback to the control system during the forming process. Once positionfeedback from the swing arms 36 indicates that the profile 20 hasarrived at its final position, the control system maintains positionand/or tension force until the profile 20 is ready to be released. Untilthat set point is reached, the control system will continue to heat andform the profile 20 around the die. Creep forming may be induced bymaintaining the profile 20 against the die 46 for a selected dwell timewhile the temperature is controlled as needed.

According to some embodiments, the profile 20 is allowed to cool at arate slower than natural cooling by adding supplemental heat via thecurrent source. This rate of temperature reduction is programmed andwill allow the profile 20 to cool while monitoring it via temperaturefeedback. Once the temperature has arrived at its final set point, forceon the profile 20 is released and the flow of current from the currentsource stops. After the force is removed from the profile 20, the jaws42 may be opened, all electrical connectors may be removed, and thefully formed base member 12 may be removed from the assembly 30.

It should be understood that, in some embodiments of the presentinvention, the base member 12 may be formed from the profile 20 using astretch forming process that does not include heating the profile 20prior to forming. Indeed, in some embodiments, the heating and coolingprocesses described above may not be utilized to form the base member12. In particular, according to some embodiments, no heat is applied tothe profile 20, whether through resistance heating by the stretchforming apparatus 30 or otherwise, and the profile 20 is formed againstthe die 46 to create the base member 12 without reaching a minimumworking temperature or otherwise controlling the temperature of theprofile 20. Thus, in such embodiments, the forming of the base member 12from the profile 20 would occur at the ambient temperature at thelocation of the stretch forming apparatus 30. But in case, whether ornot heat and/or cooling process are employed, the resultant base member12 preferably has substantially no residual stress, including, withoutlimitation, tensile residual stresses on the surface of the base member.

Once the base member 12 of the structural component 10 has been formedusing the process described above, the one or more reinforcing members14 are affixed to the base member 12. According to some embodiments,each reinforcing member 14 is affixed to the base member 12 using linearfriction welding. According to different embodiments, a single forgeaxis or a dual forge axis linear friction welding process may beutilized. This welding process allows for two (2) pieces of metal to bejoined via localized heating from friction generated from oscillatinglinear motion between the two pieces, along with a forging force whichcan be applied in one or two directions. See U.S. Pat. No. 7,624,907 toAlessi et al. for a general discussion of dual forge axis linearfriction welding, the entire contents of which are incorporated hereinby reference.

According to some embodiments, a linear friction welding machine may beutilized to accomplish the linear friction welding process. In someembodiments, the linear friction welding machine comprises a weldinghead that is operable for providing the oscillation and either singleaxis or dual axis forge loading forces that produce the welds that affixthe reinforcing members 14 to the base member 12. As shown in FIGS. 5and 6, a welding head 50 of a dual forge axis linear friction weldingmachine includes an oscillation block 52 for supporting othercomponents. According to some embodiments, two (2) Y-axis oscillationhydrostatic bearing actuators 54 are provided on opposite lateral sidesof the oscillation block 52 and are supported therein, and four (4)Z-axis forge hydrostatic bearing actuators 56 are provided on a topsurface of the oscillation block 52 for providing the forge load alongthe first forge axis, the Z-axis. Two (2) X-axis hydrostatic forgeactuators 58 are provided along one lateral side of the oscillationblock 52 for providing forge load along the second forge axis, theX-axis. Two (2) X-axis counter-load hydrostatic bearing actuators 60oppose the two (2) X-axis hydrostatic forge actuators 58 for counteringthe forge load of the X-axis forge actuators 58. Four (4) Z-axiscounter-load floating cylinders 62 are positioned about each corner ofthe oscillation block 52 for countering the load of the Z-axis forgeactuators 56. The oscillation block 52 further provides the mountingsurface for a clamping tool 64 for clamping the reinforcing members 14for oscillation. The oscillation block 52 is maintained between theY-axis hydrostatic oscillation actuators 54, the hydrostatic forge andcounter-load actuators in the X-axis, 58 and 60, and the hydrostaticforge actuators and counter load cylinders in the Z-axis, 56 and 62.Each of the plurality of hydrostatic actuators are preferably equippedwith servo-valves, for actuation, and pressure and position feedbacksensors. The hydrostatic oscillation actuators are preferably providedwith an accelerometer for velocity feedback.

According to some embodiments, in order to affix the reinforcing members14 to the base member to form the structural component 10, eachreinforcing member 14 is clamped in the welding head 50 and placed incontact with the bottom wall 16 and sidewall 18 of the base member 12,which is securely mounted in a manner to receive the reinforcing member14 in the welding head 50. As shown in FIG. 7, the reinforcing member 14is to be right-angle welded to the base member 12 along the planesdefined by interior surfaces of the bottom wall 16 and the sidewall 18,respectively. In particular, the X-axis forge actuators 58 provide aforge load along the X-axis forge axis direction. The X-axis counterload and hydrostatic bearing actuators 60 provide the counter load forceto develop the required preload on the hydrostatic bearings in theX-axis. This arrangement restrains the oscillation block 52 in theX-axis while allowing the forge actuators 58 to position and maintaincontrol in the X-axis with no load applied to the welding head 50.

The Z-axis forge actuators 56 provide a forge load along the Z-axisforge axis direction. Again, a preload is required for the hydrostaticbearings that are integral to the hydrostatic actuators. The Z-axiscounter load cylinders 62 provide a force to counter load theoscillation block's weight and the hydrostatic forge actuators' preloadto retain the oscillation block 52 in the welding head housing. Thisarrangement allows the hydrostatic forge actuators to control positionin the Z-axis with no load applied to the welding head 50. The combinedmovement of any two (2) sets of actuators provides one plane of motion.The three (3) sets of orthogonal actuators result in three (3) planes ofwelding head movement. The hydrostatic oscillation actuators providehigh-frequency reciprocating Y-axis movement of the head.

Generally regarding the dual axis forging welding process, with theoscillation block in movement, preset (conditioning) forge loads areapplied in the Z-axis and X-axis directions from zero to ninety degreesrelative to the weld interfaces, preferably substantially perpendicular.With the oscillation motion and the loads applied, the resultingfriction heats the weld interfaces to the plastic state of the material.Material is expelled from the weld interfaces, thereby cleaning the weldsurface. Each forge axis displacement is monitored by the control systemto determine the amount of material displaced, i.e., consumed, duringthe cleaning process. When the preset cleaning displacement is reached,the oscillation amplitude is reduced to zero to position the part forthe final forge motion. At or near zero oscillation, the preset finalforging load is applied in the Z- and X-axis directions. The appliedforge loads force the parts together. According to some embodiments, themagnitude of the forge load depends on the length of the weld. Forexample, in the event the weld to the sidewall is three (3) times longerthan the weld to the bottom wall, the force load required along theforge axis of the sidewall would need to be about three (3) timesgreater in magnitude than the force load along the forge axis of thebottom wall. Upon applying the forge load, the forge loading pressure isheld relatively constant. The forge displacement may be monitored andrecorded. As the material cools and solidifies the forge displacementstops. The forge load is maintained for a preset time after the forgedisplacement stops to ensure part positioning and weld quality. Thefinal welding head position may be recorded, the forge pressure isreduced to zero, the part clamp is released and the welding headretracted, thus completing the welding cycle. Thus, utilizing thejust-described dual forge axis linear friction welding process, thereinforcing members 14 are affixed to the base member 12 to form thestructural component 10.

In other embodiments, a single forge axis linear friction weldingprocess may be utilized to affix the reinforcing members 14 to the basemember 12 to form the structural component 10. Indeed, according to someembodiments, the reinforcing members 14, the tabs 22 and/or fins 24 allmay be affixed to the base member 12 using either dual forge axis linearfriction welding or single forge axis linear friction welding. Forexample, the reinforcing member 14 may be affixed to the base member 12using dual forge axis linear friction welding and the desired tabs 22and fins 24 may be affixed to the base member 12 using single forge axislinear friction welding. Rather than being right-angle welded to thebase member 12 in the space between the bottom wall 16 and sidewall 18,the tabs 22 and/or fins 24 are welded to a single plane defined by anedge of the bottom wall 16 or sidewall 18, making single forge axislinear friction welding an appropriate choice for affixing such tabs 22and/or fins 24.

Single forge axis linear friction welding is accomplished in a similarmanner to the dual forge axis linear friction welding describedhereinabove, except that only a single forge load is applied by thewelding head 60 in one direction, rather than two loads in both theX-axis and Z-axis directions. For example, there may be a single forgeload applied in the Z-axis direction. In such embodiments, the weldinghead 60 may not be equipped with X-axis forge actuators 58 or X-axiscounter load and hydrostatic bearing actuators 60. Oscillation of thecomponent to be affixed still occurs in the Y-axis direction through useof the Y-axis hydrostatic oscillation actuators 54, and the oscillationamplitude is still reduced to zero when the preset cleaning displacementis reached in order to position the component for the final forgemotion. At or near zero oscillation, the preset final forging load isapplied in the Z-axis direction only, which forces the component ontothe base member 12. Upon applying the forge load in the Z-axisdirection, the forge loading pressure is maintained for a preset timeafter the forge displacement stops to ensure part positioning and weldquality. Thus, single forge axis linear friction welding may be utilizedas an alternative or a complement to the dual forge axis linear frictionwelding described herein to affix one or more of the reinforcing members14, tabs 22, and fins 24 to the base member 12.

Advantageously, the reinforcing members 14, tabs 22, and fins 24 thatare affixed to the base member 12 may be formed of a variety of metalsand metal alloys. In this regard, the reinforcing members 14, tabs 22,fins 24 and the base member 12 may be formed of the same or differentmetals and metal alloys. In one embodiment, the base member 12 and themember being affixed to the base member 12 are each formed of an“unweldable” material, which is a material that possesses highconductivity and quickly dissipates heat away from the weld joint and/orthat exhibits cracking along the weld joint as a result of stressescaused by thermal expansion. Unweldable materials produce relativelyweak weld joints when welded using conventional fusion welding processesand, thus, are for the most part unavailable to designers ofhigh-performance, structural applications, such as the aerospaceindustry. Such materials can include titanium, aluminum, aluminumalloys, and some alloys of titanium, particularly Ti-6Al-4V, AA 2000 and7000 series alloys. Advantageously, many of these materials possessspecial corrosion, fatigue, strength, or ductility characteristics thatare desired in certain applications, particularly the aerospaceindustry.

The oscillation between the reinforcing member 14 and the base member 12(or tab 22 or fin 24, as applicable) generates sufficient frictionalheat to raise the temperature of the portions of each member adjacentthe contact area to between approximately 700° F. and a temperature justbelow the solidus of the metal forming the reinforcing member 14 and thebase member 12. Linear friction welding creates a severely deformed, buthighly refined grain structure at the weld interface with substantiallyno residual stresses. Further, linear friction welding results in anarrower heat-affected zone compared to any fusion welding process andis not limited to selected alloys with properties that are suitable forconventional welding. Linear friction welding eliminates a number ofdefects related to conventional welding, such as micro-cracks, poorductility, lack of fusion, porosity and most importantly, minimizationof distortion which can adversely effect the shape and tolerances of thejoined component members.

Thus, there has been provided improved structural components and methodsof manufacture of structural components that reduce both the amount ofraw material required and the subsequent machining operations.Advantageously, the embodiments of the base member and resultingstructural components are formed without substantial residual stressesand therefore do not exhibit the disadvantages of conventionalstructural components such as being prone to failure and/or shapechanges during further machining or use, and/or have weaker bondsbetween the base piece and the combined elements than would bepreferred.

Specific embodiments of the invention are described herein. Manymodifications and other embodiments of the invention set forth hereinwill come to mind to one skilled in the art to which the inventionpertains having the benefit of the teachings presented in the foregoingdescriptions and the associated drawings. Therefore, it is to beunderstood that the invention is not to be limited to the specificembodiments disclosed and that modifications and other embodiments andcombinations of embodiments are intended to be included within the scopeof the appended claims. Although specific terms are employed herein,they are used in a generic and descriptive sense only and not forpurposes of limitation.

What is claimed is:
 1. A method for manufacturing a structuralcomponent, the method comprising: forming a base member such that thebase member comprises at least two sidewalls and a space therebetween;hot stretch forming the base member so that the base member has apredetermined curvilinear configuration; linear friction welding atleast one reinforcing member to the at least two sidewalls so that thereinforcing member is positioned at least partially within the spacebetween the at least two sidewalls; and wherein the structural componenthas substantially no residual stress following the hot stretch formingand linear friction welding.
 2. A method according to claim 1 wherein atleast one of the base member and reinforcing member is formed oftitanium or a titanium alloy.
 3. A method according to claim 1 whereinat least one of the base member and reinforcing member is formed ofaluminum or an aluminum alloy.
 4. A method according to claim 1 whereinthe base member and reinforcing member are formed of the same material.5. A method according to claim 1 wherein the base member and reinforcingmember are formed of different materials.
 6. A method for manufacturinga structural component, the method comprising: positioning a profilecomprising at least two sidewalls and a space therebetween in aheat-insulating enclosure in which a die is disposed such that theprofile is in forming proximity to the die; resistance heating theprofile to a working temperature by passing electrical current throughthe profile; moving the profile and the die relative to each other whilethe profile is at the working temperature, thereby forming a base membercomprising the at least two sidewalls and the space therebetween andhaving a predetermined curvilinear configuration formed using hotstretch forming; mounting the curvilinear base member on a mountingassembly; affixing a reinforcing member to the at least two sidewallsusing linear friction welding so that the reinforcing member ispositioned at least partially within the space between the at least twosidewalls; and wherein the structural component has substantially noresidual stress following the hot stretch forming and linear frictionwelding.
 7. A method according to claim 6, wherein the affixing stepcomprises: positioning the reinforcing member in contact with the basemember to define a first interface between the reinforcing member and afirst sidewall and a second interface between the reinforcing member anda second sidewall; applying a first forge load at an angle relative tothe first weld interface and a second forge load at an angle relative tothe second weld interface, the first and second forge loads havingpredetermined magnitudes; oscillating the reinforcing member at apredetermined oscillation amplitude to heat the reinforcing member andthe base member; reducing the oscillation amplitude to zero; increasingthe first and second forge loads to predetermined set-points andmaintaining for a predetermined period of time; and reducing the firstand second forge loads to zero.
 8. A method according to claim 6 whereinat least one of the base member and reinforcing member is formed oftitanium or a titanium alloy.
 9. A method according to claim 6 whereinat least one of the base member and the reinforcing member is formed ofaluminum or an aluminum alloy.
 10. A method according to claim 6 whereinthe base member and reinforcing member are formed of the same material.11. A method according to claim 6 wherein the base member andreinforcing member are formed of different materials.
 12. A structuralcomponent, comprising: a base member comprising at least two sidewallsand a space therebetween, the base member having a predeterminedcurvilinear configuration formed using hot stretch forming; at least onereinforcing member linear friction welded to the at least two sidewallsso that the reinforcing member is positioned at least partially withinthe space between the at least two sidewalls; and wherein the structuralcomponent has substantially no residual stress following the hot stretchforming and linear friction welding.
 13. A structural componentaccording to claim 12 wherein at least one of the base member and thereinforcing member is formed of titanium or a titanium alloy.
 14. Astructural component according to claim 12 wherein at least one of thebase member and the reinforcing member is formed of aluminum or analuminum alloy.
 15. A structural component according to claim 12 whereinthe base member and reinforcing member are formed of the same material.16. A structural component according to claim 12 wherein the base memberand reinforcing member are formed of different materials.
 17. Astructural component, comprising: a base member, wherein the base memberis hot stretch formed by: positioning a profile comprising at least twosidewalls and a space therebetween in a heat-insulating enclosure inwhich a die is disposed such that the profile is in forming proximity tothe die; resistance heating the profile to a working temperature bypassing electrical current through the profile; and moving the profileand the die relative to each other while the profile is at the workingtemperature; and at least one reinforcing member affixed to the basemember, wherein the reinforcing member is affixed using linear frictionwelding by: positioning the reinforcing member in contact with the basemember to define a first interface between the reinforcing member and afirst sidewall and a second interface between the reinforcing member anda second sidewall; applying a first forge load at an angle relative tothe first weld interface and a second forge load at an angle relative tothe second weld interface, the first and second forge loads havingpredetermined magnitudes; oscillating the reinforcing member at apredetermined oscillation amplitude to heat the reinforcing member andthe base member; reducing the oscillation amplitude to zero; increasingthe first and second forge loads to predetermined set-points andmaintaining for a predetermined period of time; reducing the first andsecond forge loads to zero; and wherein the structural component hassubstantially no residual stress following the hot stretch forming andlinear friction welding.
 18. A structural component according to claim17 wherein at least one of the base member and the reinforcing member isformed of titanium or a titanium alloy.
 19. A structural componentaccording to claim 17 wherein at least one of the base member and thereinforcing member is formed of aluminum or an aluminum alloy.
 20. Astructural component according to claim 17 wherein the base member andreinforcing member are formed of the same material.
 21. A structuralcomponent according to claim 17 wherein the base member and reinforcingmember are formed of different materials.